Recent developments in the practice of growing legumes in an established grass sod have disclosed the inadequacies of conventional tillage apparatus, such as disk harrows, disk cultivators, rotary hoes or the like, for preparing the ground for seeding. Often the particular ground surface, in contrast with ground used for grain crops, will be uneven or rocky or with grass swards of differing thicknesses. In the preparation of such ground in sod-seeding or grassland renovation it is desirable to reduce the number of trips required over the same ground surface in order to complete the sequence of tilling, seeding, cultipacking and spraying of herbicide, and thus a premium is placed upon the efficiency of the initial tilling action. If this, for example, can be accomplished properly by means of a tilling structure drawn by a single prime mover, then equipment for carrying out the subsequent steps may be added to the same structure and the entire sod seeding procedure may be conducted during one passage over the field.
Cutting of the sward and sod matt and provision of a furrow therein of appropriate width and depth requires not only a tillage blade of special design, but also a source of power of appreciable magnitude for driving of the blade. While this power could be provided by an engine mounted on a towed vehicle, the present invention preferably employs the engine of a tractor, as for example taught by the patent to Kaller U.S. Pat. No. 2,957,529, and the tillage apparatus may be disconnected from the tractor in order to release the tractor for other uses. As will later appear, a plurality of tillage unit assemblies each having at least one blade and rotating at speeds of from 500 to 1,200 rpm have been found to be appropriate to till the sod, requiring substantially more power supplied from the tractor than required when tilling with a conventional rotary hoe or disk harrow.